See Function Reference/wp nav menu
if ( has_nav_menu( 'main_nav' ) ) {
wp_nav_menu( array('menu' => 'guest menu', 'fallback_cb' => false ));
}
See Function Reference/wp nav menu
if ( has_nav_menu( 'main_nav' ) ) {
wp_nav_menu( array('menu' => 'guest menu', 'fallback_cb' => false ));
}